Stretcher-pulleys

ABSTRACT

This stretcher-pulley associated with transmissions of internal combustion engines, comprises a roller mounted for loose rotation on a crankpin adjustable by pivoting about a fixed pin disposed eccentrically in relation to the crankpin axis under the control of resilient means constantly urging said roller against the belt to be stretched, characterised in that said crankpin is connected to the cylinder-block of the engine by means of a bearing base having substantially the same diameter as said roller and concentric thereto, said base having formed in its peripheral portion a hole in which the eccentric pivot pin rigid with the cylinder-block is fitted, a cavity being formed in said base for receiving said resilient means on the side of said base which engages said cylinder-block, an anchor stud extending through the axial portion of said crankpin, said cavity and an elongated orifice permitting the movements of said crankpin about its eccentric axis, said stud acting in actual service as a means for pressing the bearing surface of said crankpin base against said cylinder-block.

United States Patent 1191 Miokovic Mosher STRETCHER-PULLEYS [75] Inventor: Stevan Miokovic, Billancourt,

France 221 Filed: Apr. 19, 1973 211 App]. No.: 352,626

[30] Foreign Application Priority Data Apr. 28, 1972 France 72.15267 [52] 1U.S. C1. 308/18, 74/2428 [51] Int. Cl. F16c 35/00, Fl6h 7/12 [58] Field of Search 308/18; 74/2428 [56] References Cited UNITED STATES PATENTS 869,843 10/1907 Holmes et al 308/18 Primary ExaminerCharles J. Myhre I Assistant Examiner-Frank Susko Attorney, Agent, or Firm- :Stevens, Davis, Miller &

1451 Aug. 13, 1974 [57] ABSTRACT This stretcher-pulley associated with transmissions of ient means constantly urging said roller against the belt to be stretched, characterised in that said crankpin is connected to the cylinder-block of the engine by means of a bearing base having substantially the same diameter as said roller and concentric thereto, said base having formed in its peripheral portion a hole in which the eccentric pivot pin rigid with the cylinderblock is fitted, a cavity being formed in said base for receiving said resilient means on the side of said base which engages said cylinder-block, an anchor stud extending through the axial portion of said crankpin, said cavity and an elongated orifice permitting the movements of said crankpin about its eccentric axis, said stud acting in actual service as a means for pressing the bearing surface of said crankpin base against said cylinder-block.

4 Claims, 8 Drawing Figures STRETCHER-PULLEYS missions of internal combustion engines, notably those provided for driving camshafts (such as cogged-belt transmissions) which transmit relatively high torques.

As a rule, known types of belt-tighteners comprise a pulley or roller rotating loosely on a crankpin movable in translation at right angle to its axis and responsibe to resilient means constantly urging the pulley or roller against the belt for tensioning or stretching same. These resilient means may be disposed within the hollow crankpin and produce a diametral linear thrust. This known arrangement is advantageous on account of its reduced overall dimensions, but permits only a limited movement due to the room required for housing the resilient means (usually a coil spring) in the crankpin, so that only a limited stroke isallowed for the movable unit.

Other devices are known wherein the crankpin is mounted to an eccentric and the resilient means, also disposed within the crankpin, constantly urge this crankpin for rotation about its eccentric axis against the chain or belt to be tensioned. This arrangement affords a greater useful stroke without increasing the over-all dimensions in comparison with the preceding device.

Also generally, the shaft supporting the crankpin is secured by being screwed directly into the frame or housing of the machine, for example the engine cylinder-block. In this last case the considerable vibration, stresses and changes in temperature cause the screw engagement to become loose and sometimes a breakage by vibration or fatigue, generally at the point where the screw-threaded portion emerges from the cylinderblock, i.e. where the major strain concentration occurs. This risk is accentuated in the case of eccentric-type belt-tighteners or stretcher-pulleys wherein the axis of the crankpin fastening member is not coincident with the axis of rotation of the roller or pulley, thus increasing the overhang effect.

It is the essential object of the present invention to provide a stretcher-pulley of the eccentric type which is free of the above-mentioned inconveniences. This stretcher-pulley comprises a roller orpulley mounted for loose rotation on a crankpin adapted to pivot about a fixed axis disposed eccentrically in relation to the axis of said roller and containing resilient return means for tensioning the belt associated with said roller, this device being characterised in that said crankpin is connected to the cylinder-block through a bearing base of a diameter substantially equal to the roller diameter and concentric to said roller, said bearing base receiving in its outer peripheral portion the eccentric pivot pin rigid with the cylinder-block; acavity adapted to receive the aforesaid resilient means is formed in said base on the side thereof engaging said cylinder-block, and an anchoring stud extend through the axial portion of said crankpin, said cavity and an elongated orifice permitting the movements of said crankpin about its eccentric pin, said stud retaining the bearing surface of said crankpin base against the registering surface of the cylinder-block.

The base member utilized in this arrangement, owing to its greater diameter, permits on the one hand of increasing the eccentric adjustment range of the crankpin (which is thus limited only by the crankpin dimensions), and on the other hand of providing a relatively large bearing surface area for engaging the registering surface of the cylinder-block, thus eliminating any flexion stress in the central anchoring stud which operates only under a relatively moderate tractive effort, thus reducing the risk of loosening the screw engagement while eliminating the risk of breakage due to the fatigue deriving from alternate flexure stresses, which is attended by a certain detrimental overhang. Thus, the ad justment eccentricity is independent of the fastening means or members.

The possibility of loosening the screw mounting is reduced inasmuch as the inherent resiliency of the crankpin normally tends, under the influence of the tightening force, to bend its central portion and thus act as a nut'lock, while increasing the adherence of the peripheral portion of the base to the cylinder-block.

Advantage is taken of the clearing of the central portion of the surface of this base member for disposing the resilient means in a cavity of this central portion, according to a particularly satisfactory arrangement and combination of the volumes and surfaces of the crankpin and its base.

Two typical forms of embodiment of the belttightener or stretcher-pulley of this invention will now be described by way of example with reference to the attached drawing, in which:

FIG. 1 is a front elevational view of the belt-tightener according to this invention;

FIG. 2 is a section taken along the line AA of FIG.

FIG. 3 is a section taken along the line BB of FIG. 2;

" FIG. 4 is a front elevational view' of the stretcherpulley alone;

FIG. 5 is a front elevational view of a modified form of embodiment of the device of this invention;

FIG. 6 is a section taken along the line AA of FIG.

FIG. 7 is a section taken along the line BB of FIG. 6, and

FIG. 8 is a front elevational view of the stretcherpulley alone.

The stretcher-pulley illustrated. in FIGS. 1 4 of the drawings is of the eccentric type and comprises a roller or pulley 1 mounted for loose rotation on a crankpin 2 adapted to pivot about a fixed pivot pin 3 disposed eccentrically in relation to the axis of roller 1, this crankpin 2 comprising resilient return means constantly urging the device in the direction to stretch or tension the belt (not shown) passing over the roller 1. The essential feature characterising this invention lies in the fact that the crankpin is connected to the cylinderblock by means of a bearing base of a diameter corresponding substantially to that of the roller and concentric thereto, this base having formed in its peripheral portion a bore parallel to the crankpin axis which has fitted therein the eccentric pivot pin 3 rigid with the cylinder-block 4. A cavity 5 formed in the base of said crankpin is adapted to receive resilient return means. An anchoring pin 6 extends through the axial portion of crankpin 2, said cavity 5 and an elongated orifice 7, thus permitting the movements of the crankpin 2 about its eccentric pivot pin'3; the function of pin 6 is to cause the"bear'irigface of the crankpinbase to bear 7 the pin 8? permitting oftensioning the spring while preventingthis spring from rotating about the central pin 6 The'modeof operation of this device is readily apparent from the drawings and does not require a detailed description for those conversant with the art.

The modified form of embodiment illustrated in FIGS. 8 comprises most of the component elements of the first form of embodiment and departs therefrom mainly by the choice and mounting of the resilient 1. Stretcher-.pulley associated with transmissions of internal combustion engines, comprising a roller mounted for loose rotation on a crankpin adjustable by pivoting about a fixed pin disposed eccentrically in re lation to the crankpin axis under the control of resilient means constantly urging said roller against the belt to be stretched, characterised in that said crankpin is connected to the cylinder-block of the engine by means of a bearing base having substantially the same diameter as said roller and concentric thereto, said base having formed in its peripheral portion a hole in which the eccentric pivot pin rigid with the cylinder-block is fitted, a cavity being formed in said base for receiving said resilient means on the side of said base which engages said cylinder-block, an anchor'stud extending through the axial portion of said crankpin, said cavity and an r elongated orifice permitting the movements of said means consistingin this case of a coil compression spring 9 enclosed'in the pivoting crankpin 2 and a free radiallsector l0 permitting the pivotal movement due to the particular mounting of the spring 9 having one end engaged in an axial hole '11 of saidcrankpin and the other end bearing against an abutment stud 12 rigid with the cylinder block. Of course, this modified form of embodiment operates exactly like the' one shown in Although specific forms of embodiment of this invention have been described hereinabove and illustrated in the attached drawing, it will readily occur to those skilled in the art that various modifications and changes may be brought thereto without departing from the scopeof the invention as set forth in the appended 1 claims.

I claim:

crankpin about its eccentric axis, said stud acting in actual service as a means for pressing the bearing surface of said crankpin base against said cylinder-block.

2. Stretcher-pulley according to claim 1, characterised in that said resilient means consist of a coil spring having one end engaged in an axial hole of said crankpin and the other end engaged against an abutment pin rigid with the cylinder-block.

3. Stretcher-pulley according to claim 1, characterised in that said resilient means comprises a blade I spring having one end attached to an anchor pin rigid with the cylinder-block, said blade passing over an eccentric bearing pin disposed within the cavity of said crankpin base, the other end of said blade being wound on said central anchor stud.

block. b

4. Stretcher-pulley according to claim 1, characterised in that the bearing surface of said crankpin base comprises a central cavity whereby only a peripheral annular portion is caused to bear against said cylinder- 

1. Stretcher-pulley associated with transmissions of internal combustion engines, comprising a roller mounted for loose rotation on a crankpin adjustable by pivoting about a fixed pin disposed eccentrically in relation to the crankpin axis under the control of resilient means constantly urging said roller against the belt to be stretched, characterised in that said crankpin is connected to the cylinder-block of the engine by means of a bearing base having substantially the same diameter as said roller and concentric thereto, said base having formed in its peripheral portion a hole in which the eccentric pivot pin rigid with the cylinder-block is fitted, a cavity being formed in said base for receiving said resilient means on the side of said base which engages said cylinder-block, an anchor stud extending through the axial portion of said crankpin, said cavity and an elongated orifice permitting the movements of said crankpin about its eccentric axis, said stud acting in actual service as a means for pressing the bearing surface of said crankpin base against said cylinder-block.
 2. Stretcher-pulley according to claim 1, characterised in that said resilient means consist of a coil spring having one end engaged in an axial hole of said crankpin and the other end engaged against an abutment pin rigid with the cylinder-block.
 3. Stretcher-pulley according to claim 1, characterised in that said resilient means comprises a blade spring having one end attached to an anchor pin rigid with the cylinder-block, said blade passing over an eccentric bearing pin disposed within the cavity of said crankpin base, the other end of said blade being wound on said central anchor stud.
 4. Stretcher-pulley according to claim 1, characterised in that the bearing surface of said crankpin base comprises a central cavity whereby only a peripheral aNnular portion is caused to bear against said cylinder-block. 